In AV (Audio and Visual) systems including amplifier equipment, there is amplifier equipment which supports both an interface for radio communication and an interface for wired communication. This amplifier equipment is configured to be able to amplify a sound signal received at either interface and output the amplified sound signal.
Further, a technique is known in which an acquisition path of a sound signal is automatically changed to an interface for wired communication when amplifier equipment can receive the sound signal from portable information equipment at both interfaces. According to this technique, the amplifier equipment can perform stable communication with the portable information equipment, so that it is possible to make it less likely to cause a gap between an image to be displayed at display equipment and sound to be output via the amplifier equipment (see, for example, Patent Literature 1).